Contribución del ordenamiento magnético a la estabilidad y la estructura electrónica del nitruro de cromo

El efecto de la imposición del ordenamiento magnéticos en la estabilidad y la estructura electrónica en fases sólidas de nitruro de cromo (CrN) fue estudiada, basado en cálculos con la teoría del funcional densidad (DFT, siglas en inglés) y funcional híbrido no local PBE0, tal y como se implementa en el programa CRYSTAL14 -- Los cálculos fueron realizados en dos fases hipotéticas y dos fases reportadas de CrN previamente analizadas en el marco del presente proyecto -- Para analizar el efecto de los momentos magnéticos netos en la estabilidad se calculó la dispersión fonónica de la red con el fin de verificar la estabilidad dinámica del sólido -- Además se realizó un barrido de deformaciones en los modos imaginarios de algunas de las fases que resultaron inestables, con el fin de obtener estructuras nuevas más estables -- Para estudiar el efecto de los momentos magnéticos netos se calcularon las bandas de energía electrónica, la densidad de estados electrónicos (DOS, siglas en ingles) y se analizó la topología de la densidad electrónica con base en la teoría cuántica de átomos en moléculas (QTAIM, siglas en inglés) -- Se comprobó que la imposición de arreglos magnéticos tiene como primer efecto disminuir la energía de cohesión aumentando la estabilidad termodinámica de las estructuras -- Además se obtuvieron tres estructuras dinámicamente estables, una de las cuales surge de inestabilidades dinámicas y es completamente nueva -- Se observa además que la imposición de momentos magnéticos a los átomos de cromo tiene como efecto disminuir la DOS al nivel de Fermi al punto de que una de las fases estables pasa de ser un conductor a ser un semiconductor de banda prohibida indirecta -- Se evidenció cómo la DOS pone de manifiesto el arreglo de espines que existe en la estructura -- Por último fue posible mostrar cómo el tipo de enlace entre átomos no se ve afectado por la adición de un ordenamiento magnético a la estructura, además se pudo calcular el momento magnético de los átomos de cromo de estas tres fases estable

Ultimate Accuracy of Frequency to Power Conversion by Single-Electron Injection

We analyze theoretically the properties of the recently introduced and experimentally demonstratedconverter of frequency to power. The system is composed of a hybrid single-electron box with normalisland and superconducting lead, and the detector of the energy flow using a thermometer on a normalmetal bolometer. Here, we consider its potential for metrology. The errors in power arise mainly frominaccuracy of injecting electrons at the precise energy equal to the energy gap of the superconductor. Wecalculate the main systematic error in the form of the excess average energy of the injected electrons and itscumulants, and that due to subgap leakage. We demonstrate by analytic and numerical calculations that thesystematic error in detection can, in principle, be made much smaller than the injection errors, which also,with proper choice of system parameters, can be very small,Peer reviewe

Generación automática de pruebas de validación de prácticas de sistemas distribuidos

La corrección de prácticas de sistemas distribuidos es una tarea costosa para el profesor que evalúa dichos ejercicios. Esta tarea puede ser sistematizada mediante la ejecución de tests automatizados cuya elaboración representa una alta inversión de tiempo para cada práctica a corregir. Así surge la necesidad de desarrollar una herramienta que, a partir de pequeñas especificaciones proporcionadas por el usuario, genere fácil y rápidamente dichos scripts libres de errores de sintaxis. Con este fin, se ha desarrollado una herramienta web flexible, sencilla de utilizar y que permite ahorrar tiempo dedicado a la elaboración de scripts.Peer Reviewe

Role of the interfacial water structure on electrocatalysis: Oxygen reduction on Pt(1 1 1) in methanesulfonic acid

Most of electrocatalytic reactions occur in an aqueous environment. Understanding the influence of water structure on reaction dynamics is fundamental in electrocatalysis. In this work, the role of liquid water structure on the oxygen reduction at Pt(1 1 1) electrode is analyzed in methanesulfonic (MTSA) and perchloric acids. This is because these different anions can exert a different influence on liquid water structure. Results reveal a lower ORR electrode activity in MTSA than in HClO4 solutions and they are discussed in light of anion's influence on water structural ordering. From them, the existence of an outer-sphere, rate determining, step in the ORR mechanism is suggested.This work has been carried out under MINECO project CTQ2013-44083-P (Spain). APSR acknowledges the scholarship “Estudiantes sobresalientes de posgrado” at the UNAL and COLCIENCIAS National Doctoral Scholarship (567). MFS acknowledges the support of UNAL (Research Project 19030)

Generación automática de pruebas de validación de prácticas de sistemas distribuidos

La corrección de prácticas de sistemas distribuidos es una tarea costosa para el profesor que evalúa dichos ejercicios. Esta tarea puede ser sistematizada mediante la ejecución de tests automatizados cuya elaboración representa una alta inversión de tiempo para cada práctica a orregir. Así surge la necesidad de desarrollar una herramienta que, a partir de pequeñas especificaciones proporcionadas por el usuario, genere fácil y rápidamente dichos scripts libres de errores de sintaxis. Con este fin, se ha desarrollado una herramienta web flexible, sencilla de utilizar y que permite ahorrar tiempo dedicado a la elaboración de scripts

Bolometric detection of coherent Josephson coupling in a highly dissipative environment

The Josephson junction is a building block of quantum circuits. Its behavior, well understood when treated as an isolated entity, is strongly affected by coupling to an electromagnetic environment. In 1983 Schmid predicted that a Josephson junction shunted by a resistance exceeding the resistance quantum $\mathbf{\textit{R}}_\mathrm{Q} = h/4e^2 \approx 6.45$ k$\mathbf{\Omega}$ for Cooper pairs would become insulating since the phase fluctuations would destroy the coherent Josephson coupling. Although this prediction has been confirmed in charge transport experiments, recent microwave measurements have questioned this interpretation. Here, we insert a small junction in a Johnson-Nyquist type setup, where it is driven by weak current noise arising from thermal fluctuations. Our heat probe minimally perturbs the junction's equilibrium, shedding light on features not visible in charge transport. We find that while charge transport through the junction is dissipative as expected, thermal transport is determined by the inductive-like Josephson response, unambiguously demonstrating that a supercurrent survives even deep into the expected insulating regime. The discrepancy between these two measurements highlights the difference between the low frequency and the high frequency response of a junction and calls for further theoretical and experimental inputs on the dynamics of Josephson junctions in a highly dissipative environment.Comment: Typo corrected in the ending discussion, with added discussion on the results of ref.[16] cited in the main tex

Comunidades, territorios y turismo en América Latina

Este libro es una suerte de regreso al futuro en la medida que intenta explicar la historia reciente del desarrollo turístico como parte de los males del capitalismo neoliberal globalizado, y al mismo tiempo tornar palpable las ventajas y oportunidades de ese otro turismo, enraizado en los paisajes naturales y culturales de las comunidades locales

Role of age and comorbidities in mortality of patients with infective endocarditis

Purpose: The aim of this study was to analyse the characteristics of patients with IE in three groups of age and to assess the ability of age and the Charlson Comorbidity Index (CCI) to predict mortality. Methods: Prospective cohort study of all patients with IE included in the GAMES Spanish database between 2008 and 2015. Patients were stratified into three age groups:<65 years, 65 to 80 years, and = 80 years.The area under the receiver-operating characteristic (AUROC) curve was calculated to quantify the diagnostic accuracy of the CCI to predict mortality risk. Results: A total of 3120 patients with IE (1327 < 65 years;1291 65-80 years;502 = 80 years) were enrolled.Fever and heart failure were the most common presentations of IE, with no differences among age groups.Patients =80 years who underwent surgery were significantly lower compared with other age groups (14.3%, 65 years; 20.5%, 65-79 years; 31.3%, =80 years). In-hospital mortality was lower in the <65-year group (20.3%, <65 years;30.1%, 65-79 years;34.7%, =80 years;p < 0.001) as well as 1-year mortality (3.2%, <65 years; 5.5%, 65-80 years;7.6%, =80 years; p = 0.003).Independent predictors of mortality were age = 80 years (hazard ratio [HR]:2.78;95% confidence interval [CI]:2.32–3.34), CCI = 3 (HR:1.62; 95% CI:1.39–1.88), and non-performed surgery (HR:1.64;95% CI:11.16–1.58).When the three age groups were compared, the AUROC curve for CCI was significantly larger for patients aged <65 years(p < 0.001) for both in-hospital and 1-year mortality. Conclusion: There were no differences in the clinical presentation of IE between the groups. Age = 80 years, high comorbidity (measured by CCI), and non-performance of surgery were independent predictors of mortality in patients with IE.CCI could help to identify those patients with IE and surgical indication who present a lower risk of in-hospital and 1-year mortality after surgery, especially in the <65-year group

Role of age and comorbidities in mortality of patients with infective endocarditis

[Purpose]: The aim of this study was to analyse the characteristics of patients with IE in three groups of age and to assess the ability of age and the Charlson Comorbidity Index (CCI) to predict mortality. [Methods]: Prospective cohort study of all patients with IE included in the GAMES Spanish database between 2008 and 2015.Patients were stratified into three age groups:<65 years,65 to 80 years,and ≥ 80 years.The area under the receiver-operating characteristic (AUROC) curve was calculated to quantify the diagnostic accuracy of the CCI to predict mortality risk. [Results]: A total of 3120 patients with IE (1327 < 65 years;1291 65-80 years;502 ≥ 80 years) were enrolled.Fever and heart failure were the most common presentations of IE, with no differences among age groups.Patients ≥80 years who underwent surgery were significantly lower compared with other age groups (14.3%,65 years; 20.5%,65-79 years; 31.3%,≥80 years). In-hospital mortality was lower in the <65-year group (20.3%,<65 years;30.1%,65-79 years;34.7%,≥80 years;p < 0.001) as well as 1-year mortality (3.2%, <65 years; 5.5%, 65-80 years;7.6%,≥80 years; p = 0.003).Independent predictors of mortality were age ≥ 80 years (hazard ratio [HR]:2.78;95% confidence interval [CI]:2.32–3.34), CCI ≥ 3 (HR:1.62; 95% CI:1.39–1.88),and non-performed surgery (HR:1.64;95% CI:11.16–1.58).When the three age groups were compared,the AUROC curve for CCI was significantly larger for patients aged <65 years(p < 0.001) for both in-hospital and 1-year mortality. [Conclusion]: There were no differences in the clinical presentation of IE between the groups. Age ≥ 80 years, high comorbidity (measured by CCI),and non-performance of surgery were independent predictors of mortality in patients with IE.CCI could help to identify those patients with IE and surgical indication who present a lower risk of in-hospital and 1-year mortality after surgery, especially in the <65-year group

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality